Spiral Bragg grating waveguides for TM mode silicon photonics.

Area of Science:

• Photonics and optical engineering
• Integrated optics
• Semiconductor device fabrication

Background:

• Silicon-on-insulator (SOI) platform is a key technology for integrated photonics.
• Bragg grating waveguides (BGWs) are essential components for wavelength filtering and control.
• Spiral designs offer space efficiency in integrated optical circuits.

Purpose of the Study:

• To demonstrate spiral Bragg grating waveguides (BGWs) for the fundamental transverse magnetic (TM) mode on the SOI platform.
• To compare the performance of TM spiral waveguides against transverse electric (TE) spiral waveguides.
• To investigate the impact of space-efficient design on device performance and fabrication tolerances.

Main Methods:

• Fabrication of spiral Bragg grating waveguides on a silicon-on-insulator (SOI) platform.
• Characterization of propagation losses for both TM and transverse electric (TE) modes.
• Analysis of device bandwidth, extinction ratio (ER), and group delay slope.

Main Results:

• TM spiral waveguides exhibit lower propagation losses compared to TE counterparts.
• Space-efficient spiral BGWs (131×131 µm² for 4 mm length) show reduced susceptibility to fabrication non-uniformities.
• Achieved narrow bandwidths (as low as 0.09 nm) and high extinction ratios (up to 52 dB).
• Demonstrated a TM chirped spiral Bragg grating waveguide with a negative group delay slope (-11 ps/nm).

Conclusions:

• Spiral BGWs on SOI are a promising technology for compact and high-performance photonic devices.
• The TM mode offers advantages in terms of lower propagation loss for spiral BGWs.
• The demonstrated devices are suitable for applications requiring precise spectral control and dispersion management in integrated photonic systems.